Analysis Of The Sedimentary Background And Geological Significance Of Late Paleozoic In Nixiong Region,Tibet

The late Paleozoic of Gangdisi in the Lhasa terrane has always been a hot topic in the study of Qinghai-tibet plateau.The late Paleozoic includes the Yongzhu Formation in the littoral and shallow sea,the Laga Formation in the nearshore and shelf ice sea,the Angjie Formation in the shelf ice sea and theXiala Formation in the open platform.The late Paleozoic is an important transition period of the geological evolution of the Lhasa terrane.In this paper,in late Paleozoic Yongzhu Formation and Laga Formation as the research object,by means of the measured stratigraphic section,through to the explain of sedimentary environment,Yongzhu Formation set of detrital zircon,geochemical analysis of the Laga Formation and seismolith analysis of the Laga Formation,Combined with the previous understanding of the late Paleozoic tectonic background of the Lhasa terrane,The sedimentary background and geological significance of late Paleozoic in Nixiong area,Tibet were discussed.1.The thesis research purpose and meaning: by field measured section survey,detrital zircon U-Pb age characteristics,geochemical analysis,a comprehensive understanding of late Paleozoic Yongzhu Formation and Laga Formation rock composition,structural characteristics,and The sedimentary environment was also explained,In order to provide the basis for the late Paleozoic geological characteristics in Nixiong area of Lhasa terrane.2.The main contents of this paper are as follows: Based on the field survey of the Yongzhu Formation of upper carboniferous and the Laga Formation of upper carboniferous and lower Permian in the western Lhasa terrane,the analysis of detrital zircons of the Yongzhu Formation,the geochemical analysis of the Laga Formation,and a brief description of the seismolites were made.The sedimentary background and geological significance of the late Paleozoic in Lhasa terrane are revealed by combining with previous investigations.3.Conclusion: according to the field profile survey and the sedimentary sequence division,the Yongzhu Formation is a set of shore-shallow sea clastic sedimentary environment,and the Laga Formation is a set of shore depositional and outwash drip sedimentary assemblage;By comparing the age characteristics of the detrital zircons in the Yongzhu Formation with the peripheral microlandmasses,it is concluded that the Yongzhu Formation has the provenance characteristics of the Indian side of Gondwanaland continent,and is significantly related to the Qiangtang,Lhasa and Himalayan microlandmasses in southern China.The geochemical analysis of the Laga Formation and the seismolites shows that the Laga Formation sedimentary facies and the clastic rock geochemical source area do not contain the materials from the inner Lhasa terrane,but come from the northern margin of Gondwana continent to the south,and the clastic components may have undergone multiple reconveyance,showing a mature continental source area.The seismite of the Laga Formation has typical lithology and structural characteristics.The vertical sedimentary sequence of the Laga Formation seismite unit is determine.